The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2001-231355 filed on Jul. 31, 2001 the entire contents thereof is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an output shaft structure of a personal watercraft.
2. Description of Background Art
Personal watercrafts of a type shown in FIG. 12 have been known, wherein an engine 1 is mounted on a watercraft 2 with a crankshaft 1a of the engine 1 extending along the longitudinal direction of the watercraft body 2, and a shaft 3a of a jet pump 3 is coupled via a coupler 4 to an rear end 1b of the crankshaft 1a in such a manner as to be disposed on an extension of the crankshaft 1a. 
In these personal watercrafts, power from the crankshaft 1a of the engine 1 is transmitted to the jet pump 3 via the shaft 3a, to propel the watercraft body 2.
The above-described personal watercrafts have been frequently used for the purpose of enjoying leisure sport, and as a result of immoderate running of the watercrafts, water may be somewhat permeated in the watercraft body 2.
Accordingly, in the above-described related art personal watercraft, there has arisen a problem that water permeates into the watercraft body 2 and comes in contact with the coupler 4, is dispersed in the watercraft body 2 by a centrifugal force of the coupler 4 having a diameter larger than that of each of the crankshaft 1a and the shaft 3a. 
Further, in the personal watercrafts of this type, piping for taking off cooling water is connected to a portion, on the upstream side from an impeller, of the jet pump, and cooling water is supplied to the engine or the like via the piping. As a result, there problems have arisen wherein the piping may interfere with the coupler 4 having a large diameter, and that the piping is liable to deteriorate due to the fact that the piping is exposed to water (particularly, sea water) dispersed by the centrifugal force of the coupler 4.
Accordingly, a first object of the present invention is to solve the above-described problems and to provide an output shaft structure of a personal watercraft, which is capable of preventing the dispersal of water in a watercraft body, preventing interference of piping with a coupler, and preventing the piping from deteriorating.
Two-cycle engines have been used as power sources of general personal watercrafts. However, in recent years, to meet a requirement to lower environmental pollution, personal watercrafts using four-cycle engines as power sources have been proposed (Japanese Patent No. 2880691).
Outputs of four-cycle engines are smaller than those of two-cycle engines as compared with the same displacement, and to cope with such an inconvenience, it has been examined to develop personal watercrafts in which engines with turbo-chargers are mounted. For example, the present inventor has already proposed, in Japanese Patent Laid-open No. 2001-140641, a personal watercraft in which an engine with a turbo-charger is mounted.
A turbo-charger has a relatively large weight, and therefore, from the viewpoint of keeping a good weight balance of a watercraft, the turbo-charger may be desired to be provided near an engine, more specifically, immediately behind the engine. Even in Japanese Patent Laid-open No. 2001-140641, a turbo-charger is disposed immediately behind an engine 2, and consequently, the turbo-charger is disposed immediately over a coupler.
Such a personal watercraft provided with a turbo-charger, however, has an inconvenience wherein, as described above, water dispersed by the coupler directly comes into contact with the turbo-charger, so that a casing of the turbo-kept charger kept at a high temperature is liable to be thermally fatigued.
Accordingly, a second object of the present invention is to provide an output shaft structure of a personal watercraft, which is capable of suppressing a casing of a turbo-charger from being thermally fatigued.
To achieve the above first object according to the present invention there is provided an output shaft structure of a personal watercraft, wherein an engine is mounted on a watercraft body with a crankshaft of the engine extending along the longitudinal direction of the watercraft body and a shaft of a jet pump is coupled via a coupler to a rear end of the crankshaft in such a manner as to be disposed on an extension of the crankshaft. The output shaft structure includes a coupler cover that is provided for covering the coupler, and piping for cooling water, which is communicated to the jet pump, is fixed onto the coupler cover.
To achieve the above first and second objects of the present invention a turbo-charger is disposed over the coupler, and the piping is fixed onto the coupler cover at a position between the coupler cover and the turbo-charger.
To achieve the above second object of the present invention there is provided an output shaft structure of a personal watercraft, wherein an engine is mounted on a watercraft body with a crankshaft of the engine extending in the longitudinal direction of the watercraft body, a shaft of a jet pump is coupled via a coupler to a rear end of the crankshaft in such a manner so as to be disposed on an extension of the crankshaft, and a turbo-charger is disposed over the coupler. The output shaft structure includes a coupler cover formed into an approximately inverse U-shape in cross-section that is provided for covering the coupler, and the coupler cover is turnable around the shaft of the jet pump.
According to the present invention a rear portion of the coupler cover is connected to a bearing member for turnably supporting the shaft of the jet pump on the watercraft body, a breather hose and/or a grease supply hose are/is connected to the bearing member, and a cutout portion for allowing the turning of the coupler cover without interference with the breather hose and/or grease supply hose is formed in the rear portion of the coupler cover.
According to the output shaft structure of a personal watercraft of the present invention an engine is mounted on a watercraft body with a crankshaft of the engine extending along the longitudinal direction of the watercraft body and a shaft of a jet pump is coupled via a coupler to a rear end of the crankshaft in such a manner as to be disposed on an extension of the crankshaft. This output shaft structure includes a coupler cover that is provided for covering the coupler, and piping for cooling water, which is communicated to the jet pump, is fixed onto the coupler cover. With this structure, even if water, which has been permeated in the watercraft body and comes in contact with the coupler, is dispersed by the coupler, the water thus dispersed can be blocked by the coupler cover provided for covering the coupler.
Since the coupler is covered with the coupler cover, the piping for cooling water does not interfere with the coupler.
Since the dispersal of water is blocked by the coupler cover, the piping is exposed to water to a lesser extent, with a result that the piping is less deteriorated.
Since the piping is fixed on the coupler cover, that is, in a state being floated from the bottom shell, the piping is less exposed to water having been permeated in the watercraft body. As a result, it is possible to more certainly prevent deterioration of the piping.
According to the output shaft structure of a personal watercraft according to the present invention a turbo-charger is disposed over the coupler, and the piping is fixed onto the coupler cover at a position between the coupler cover and the turbo-charger. Accordingly, the output shaft structure has the following functions and effects:
Since the dispersal of water by the coupler is blocked by the coupler cover, the turbo-charger is less exposed to water dispersed by the coupler. As a result, it is possible to improve durability of the turbo-charger.
Also, since the piping is fixed on the coupler cover at a position between the coupler cover and the turbo-charger, it is possible to obtain an effect wherein the piping for cooling water can be disposed by making use of a space between the coupler cover and the turbo-charger. Further, since the piping is disposed on the coupler cover, the piping does not come in contact with the turbo-charger kept at a high temperature, with a result that the piping is less deteriorated.
According to the output shaft structure of a personal watercraft according to the present invention an engine is mounted on a watercraft body with a crankshaft of the engine extending in the longitudinal direction of the watercraft body, a shaft of a jet pump is coupled via a coupler to a rear end of the crankshaft in such a manner as to be disposed on an extension of the crankshaft, and a turbo-charger is disposed over the coupler. This output shaft structure includes a coupler cover formed into an approximately inverse U-shape in cross-section that is provided for covering the coupler, and the coupler cover is turnable around the shaft of the jet pump. With this structure, since the dispersal of water by the coupler is blocked by the coupler cover, the turbo-charger is not exposed to the water dispersed by the coupler. As a result, it is possible to improve the durability of the turbo-charger.
Since the coupler cover is formed into an approximately inverse U-shape and is turnable around the shaft of the jet pump, the coupler cover is removed in a direction perpendicular to the shaft of the jet pump by turning the coupler cover around the shaft of the jet pump.
That is to say, the coupler cover can be removed, in the narrow, restricted inner space of the watercraft body, without movement of the coupler cover in the direction along the shaft of the jet pump and also without interference with the turbo-charger.
Accordingly, only the coupler cover can be removed without removal of the turbo-charger and the coupler can be inspected and repaired.
According to the output shaft structure of a personal watercraft according to the present invention a rear portion of the coupler cover is connected to a bearing member for turnably supporting the shaft of the jet pump on the watercraft body. As a result, the coupler cover can be mounted in a stable state.
Also, in this structure, a breather hose and/or a grease supply hose are/is connected to the bearing member. As a result, expanded air generated in the bearing portion can escape through the breather hose, and/or grease can be supplied to the bearing portion through the grease supply hose.
Further, in this output shaft structure, a cutout portion for allowing the turning of the coupler cover without interference with the breather hose and/or grease supply hose is formed in the rear portion of the coupler cover. As a result, only the coupler cover can be removed by turning the coupler cover without removal of the hose, and the coupler can be inspected and repaired.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.